The rich play with fire and the poor get burned. That sums up a report issued March 31 by the U.N. Intergovernmental Panel on Climate Change (IPCC) about the worsening risks of climate change. Yet even rich nations will face serious challenges. "Nobody on this planet is going to be untouched by climate change," said IPCC chair Rajendra Pachauri at a press conference releasing the report in Yokohama, Japan.

According to Pachauri and the hundreds of scientists who prepared the report, climate change is no longer something that will happen in the future. It is already here, and it is already impacting people on all seven continents and seven seas. The world now has a different climate than it had only a few decades ago, thanks to fossil fuel burning, forest clearing and other human activities.

As a result, the need for nations everywhere to adapt is already here, according to the report of the second team of IPCC scientists (known as Working Group II), who assessed more than 12,000 scientific papers to deliver an authoritative consensus on the impacts of climate change, the vulnerabilities of society and the natural world, as well as how we might adapt to a changed climate. "We see impacts from the equators to the poles and the coast to the mountains," noted biologist Christopher Field of Stanford University, co-chair of Working Group II at the press event.

The opportunity to prevent catastrophic global warming has not disappeared, even if the world has burned through half the fossil fuels it can, according to the first team of IPCC scientists who assessed the fundamental physics of climate change and released their report in September. But the world must drop its carbon habit soon. Since 1880, 531 gigatons of carbon have been emitted, and the IPCC scientists estimate that no more than 800 gigatons should be emitted for a better-than-even chance of keeping global warming below 2 degrees Celsius. If warming rises beyond that threshold, the scientists say, serious harm will be done to ecosystems and societies everywhere. The more warming, the greater the risk of "severe, pervasive and irreversible impacts," the new report states.

Unfortunately, in just the time between this report and the last iteration in 2007, climate change has grown 40 percent stronger thanks to ever increasing emissions of greenhouse gases. Already, the world has warmed 0.85 degree C since 1880. Global warming is now "unequivocal" and concentrations of CO2 have reached levels "unprecedented in at least the last 800,000 years." Or as Michel Jarraud, secretary-general of the World Meteorological Organzation put it at the press conference: "Ignorance is no longer an excuse. We know."

In that light, climate change becomes a risk management proposition, particularly given the uncertainty about exactly how bad impacts might become and when. The worst risks include sea level rise for small islands and coasts, flooding, the breakdown of infrastructure in the face of extreme weather, loss of livelihoods for farmers and fishers, food insecurity and heat-wave deaths. Expect a big demand for energy for air conditioning as the 21st century continues.

Some of these impacts are already here, from a meltdown of polar ice and glaciers everywhere to higher rates of sea level rise than the IPCC predicted in the past. Crops, such as wheat and maize (corn), have been hurt more by heat waves and drought than helped by higher levels of CO2, which can sometimes permit more luxuriant plant growth. Some crop yields in places like northern Europe and southeastern South America where drought has not set in have actually improved.

The bad outweighs the good to date. Reductions in yields of wheat and maize have already had an impact on food prices, and some argue on the stability of nations as well. Extreme weather—from floods to wildfires—continues to take an increasing toll, and climate change will likely exacerbate existing health problems such as malaria and heat stroke. The biggest impact may prove to be changes to the availability of fresh water. All of these hazards, laid out in detail in the new report, afflict the poorest the most, particularly subsistence farmers throughout the world who depend on consistent rains for adequate food. "They are threatened in their very existence," Pachauri argued at the press conference.

Climate change will also raise the risk of conflict, whether civil war or fights between nation states over critical resources or boundaries, according to the new report. In short, climate change will make remedying existing poverty that much harder.

Opportunities still exist for adaptation, however. Communities, cities, states and nations have begun to adapt, whether improved water management in San Diego, Calif., or planting mangroves to stabilize seashores in the island nation of Tuvalu. Cimate change can be ameliorated both by cutting back on the pollution that causes it as well as by improving society to decrease vulnerability.

The natural world has had to adapt as well, with animals and even plants moving or shifting seasonal behaviors or migration. Some marine animals have shifted their range by as much as 400 kilometers in pursuit of equally cold climes, and ocean acidification is accelerating. As the climate continues to change, species will face even greater challenges, and many may go extinct as global warming tips them into disaster when paired with other threats such as habitat loss. Entire ecosystems will be transformed, like the march of shrubs into the former tundra of Siberia and North America. "We may already be on the threshold or over the threshold of the sixth mass extinction in earth's history," Field noted.

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